Women and science and nature and nurture

A little while ago Harvard University president Lawrence Summers gave a speech in which he suggested that underrepresentation of women in math and natural sciences might be partially due to the differences in men's and women's innate abilities, and all the hell broke loose.

First of all, if this were true (I don't know whether or not it is, and I suppose Summers doesn't either) it would bother me a fair lot on some level. I am not quite sure why. It's not like it would diminish women in science as such - it would just mean that, say, 8% of men have what it takes to be a scientist, but only 6% of women, or something like that, but it would bother me anyway, and apparently it bothers a lot of other people. And the other thing that bothers me is that even if it were true it would still be a thing one is not supposed to mention in speeches or talk about in a polite society. And, for example, if someone were to prove that fewer women have the aptitude for science than men, that someone would be in a fair lot of trouble.

I decided to look up the enrollment statistics for the Faculty of Science of the University of Helsinki. Found the statistics for the end of 2002. 80% of biochemitry students, 77% of biology students, 30% of physics students, 66% of chemistry students, 40% of math students and 19% of comuter science students are women. These are very big differences, both between sexes and between fields. I can't offhand think of any differences between cognitive skills needed to study chemistry and physics. I find it quite difficult to believe that there is some innate difference between men and women that makes men study physics and women study chemistry. I also find it difficult to think of any kind of discriminating that would keep women out of physics and men out of chemistry. So why are the sex ratios so different?